From DC, go up 295 about 40 miles until you get to MD 32. Take 32 east and look out your left window. You can wave at the NSA buildings, especially the black mirrored ones...
There's a lot of stuff there for just one day.
If you've got wheels, Mt. Vernon is quite interesting. The Naval Academy in Annapolis is also worth a trip.
From DC, go up 295 about 40 miles until you get to MD 32. Take 32 east and look out your left window. You can wave at the NSA buildings, especially the black mirrored ones...